Olesen fired eight birdies and an eagle in a superb 62 to reach the halfway stage of the €6.5m event on 15 under, six shots clear of Spain’s Adrian Otaegui and Thailand’s Thongchai Jaidee.
With the Regnum Carya Golf Resort & Spa hosting the tournament for the first time, Otaegui’s 63 had earlier eclipsed the course record established by first-round leader George Coetzee, who could only add a 73 to his opening 64.
Willett, who needs to finish outright fifth or better to reclaim top spot in the Race to Dubai from Henrik Stenson, fared even worse, with a 74 which left him 16 shots off the lead and in a tie for 58th in the 78-man field.
Olesen was in contention for a Ryder Cup place after winning the Dunhill Links Championship last year and making a strong start to this season, but missed the cut in seven of his last 10 events.
The 26-year-old was invited to Hazeltine by fellow Dane Thomas Bjorn, one of European captain Darren Clarke’s vice-captains, and now has extra motivation to qualify for the team which will try regain the trophy in Paris in 2018.
“It was a great experience,” Olesen said. “In the beginning it was a little bit difficult to be there when I had a pretty good chance in the summer to make the team, but I felt like I learned a lot being around the captain and the vice-captains.
“One of my goals is to make the team and if I make it, I will be more prepared and know a little bit of what I’m going into. It’s so different from any other tournament and I realised that when I got there.
“It’s so much bigger than you think and I was standing on that first tee on Friday to see the atmosphere there. Some of the stuff (shouted by fans) was very personal and I thought it was hard for the players. I’m happy I saw that because that’s how it going to be in America in future.”
Willett’s Ryder Cup debut ended in disappointment after three defeats in three matches amid the furore caused by an article written by his brother Pete which criticised the behaviour of American fans.
And the 29-year-old is also in danger of missing out on the Race to Dubai title for a second year in a row after failing to card a single birdie in his second round in Antalya.
Willett refused to speak to reporters at the end of his second round, but later tweeted: “Well this game is really kicking me in the nuts at the minute!! If it’s not one thing it’s another.. Haha.. #grinditout.”